Graphene Oxide–TiO2 Nanocomposite Films for Electron Transport Applications

Abstract

Graphene oxide–titanium dioxide (GO–TiO2) nanocomposite thin films were prepared for application as the window layer of perovskite solar cells. Graphene oxide (GO) was prepared by a modified Hummer’s method, and titanium dioxide (TiO2) nanoparticles were synthesized by hydrothermal solution method. Thin films of GO–TiO2 nanocomposite were prepared with different wt.% of GO by spin coating on indium tin oxide (ITO) substrate followed by annealing at 150°C. X-ray diffraction analysis revealed rutile phase of TiO2 nanostructures. The bandgap of the pure TiO2 thin film was found to be 3.5 eV, reducing to 2.9 eV for the GO–TiO2 nanocomposites with a red-shift towards higher wavelength. Furthermore, thermal postannealing at 400°C improved the transparency in the visible region and decreased the sheet resistance. Morphological and elemental analysis was performed by scanning electron microscopy and energy-dispersive x-ray spectroscopy, respectively. The current–voltage characteristic of the GO–TiO2 nanocomposites indicated Ohmic contact with the ITO substrate. The chemical composition of the as-synthesized GO–TiO2 nanocomposites was investigated by x-ray photoelectron spectroscopy (XPS). The results presented herein demonstrate a new, low-temperature solution-processing approach to obtain rGO–TiO2 composite material for use as the electron transport layer of perovskite solar cells.